Barrier arrangement for arc chute which stretches arcs in both vertical and horizontal planes



Aug. 24, 1965 Filed Aug. l5, 1960 L. 3a BARRIER ARRANGEMENT FOR ARC CHUTE WHICH STRETCHES ARCS IN BOTH VERTICAL AND HORIZONTAL PLANES 2 Sheets-Sheet l A. BURToN 202,790

Aug. 24, 1965 A BURTON 3 202,790

L. BARRIER ARRANGEMENT FOR ARC CHUTE WHICH STRETCHES ARCS IN BOTH VERTICAL AND HORIZONTAL PLANES 2 Sheets-Sheet 2 Filed Aug. l5. 1960 United States Patent 3,202,790 BARRlER ARRANGEMENT FR ARC CHUTE WHICH STRETCHES ARCS EN BOTH VERTI- CAL AND HORHZNTAL PLANES Lawrence A. Burton, (lconornowoe, Wis., assigner' to Allis-"Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Aug. 15, 196i), Ser. No. 49,550 '7 Claima (Cl. Zilli-144) This invention relates tocircuit interrupters. More speciiically this invention relates to an improved arc chute for extinguishing an are in a circuit interrupter.

Circuit interruption ordinarily proceeds in two steps. First, a pair of current carrying contacts separate and form an arc of hot ionized material that maintains the circuit between the contacts. Then an arc chute and associated equipment operate on the arc medium to restore its dielectric strength and thereby extinguish the arc. One

v type of aro chute comprises basically a boxlilte structure of insulating material that is somewhat flattened so as to extend principally in the two transverse directions of arc movement and contact separation. The relatively closely spaced sides of the arc chute support barriers that cool and constrict the arc and progressively loop the arc back and forth in the relatively restricted third transverse direction, between the sides of the chute. ln most cases the arc chute extends somewhat beyond the arc extinguishing region so as to further cool and deionize the dielectric medium sufficiently to prevent the arc residue from causing a flashover at the exhaust end of the chute.

The arc chute of this invention loops the arc back and forth between the relatively closely spaced side walls of the arc chute, and it also inclines the loops of the arc toward the relatively unrestricted direction of arc movement so that each of the loops of the arc stretches from one side near the receiving end of the arc chute to the other side nearer the exhaust end of the arc chute. Since the direction of arc travel is relatively unrestricted, the arc lengthening and extinguishing action of this arc chute is very much improved over arc chutes of the prior art. Circuit interrupters using this arc chute are substantially reduced in height over circuit interrupters of similar rating which use prior art arc chutes. ln addition, including the loops in the direction of arc movement produces a blowout action because the magnetic elds of the loops are thus favorably oriented to drive the arc into the arc chute.

This arc chute has an array of arc control barriers that fold the arc into a succession of loops; and as the arc moves farther into the chute, the barriers restrict the crests of the arc loops somewhat more along one side of the chute than along the other side. The crests of the arc loops move somewhat more freely along the less restricted sides of the arc chute, and the arc inclines toward the exhaust along the less restricted side.

One object of this invention is to provide a new and improved circuit interrupter.

Another object of this invention is to provide a new and improved arc chute.

Another object of ths invention is to provide an arc chute that requires only a relatively small space to satisfactorily lengthen and extinguish an arc.

Another object of this invention is to provide an arc chute in which the magnetic eld that is associated with the arc helps drive the arc into the chute.

Another object of this invention is to provide a new and improved arc chute in which an arc is relatively restricted on one side of the arc chute `and is relatively unrestricted along the other side.

Other objects and advantages of this invention will appear as the arc chute and a circuit interrupter are explained.

FlG. 1 in the drawing is a side View `of a circuit interrupter and illustrates the relationship between the improved arc chute and the other elements of the circuit interruptor;

FlG. 2 is a top view of the circuit interrupter and the arc chute of FIG. 1;

FIGS. 3 and 4 together show the arc chute of FIGS. l and 2 with two half-sections of the arc chute opened to show the details of the arc control barriers;

FIG. 5 is a partial section of the arc chute taken along lines V--V in FIG. l and shows two of the barriers of FlGS. 3 and 4 when the half-sections of the arc chute are in place.

The speciiic circuit interrupter of FlGS. l and 2 is usually called a contactor, and it is intended to open and close the circuit of a motor or similar load. The contactor controls the circuit between two xed Contact assemblies lil and l2. A movable contact assembly 14 bridges the two fixed contact assemblies in one operating position and completes the circuit. ln the operating position that FIG. l illustrates, the movable contact assembly lltis separated from the two iixed contact assemblies le, 12 and the circuit is interruped. Each of the two fixed contact assemblies is adapted at one end to form a terminal 116 of the contactor and is provided at the other end with inserts 17 of a material that is suitable to withstand the arcing that occurs when the contactor opens. rl`he iixed contact assembly 12 includes a coil i9 that produces a magnetic lield so long as the contactor carries current. A magnetic core 20 mounted inside the coil i9 and two magnetic pole pieces 21 direct the magnetic field of the coil to the arc forming and extenguishing regions of the contactor where the magnetic eld helps to drive an arc into .the chute. The movable contact assembly ld includes a movable contact 23 with two contact inserts 24, an operating shaft 26, an assembly 27 for mounting the movable contact on the operating shaft, and an assembly 29 for suitably mounting the operating shalt to swing the movable contact open and closed. The movable contact 23 is shaped somewhat like a pair of horns, and an arc that forms initially between each pair of inserts 17, 24 tends to move rapidly out toward the tips of the horns and then to join as a. single arc. Thus in the contactor of FlG. l the direction of contact separation and arc lengthening is defined by the two iixed contact assemblies rather than by the direction that movable contact assembly 14 travels.

The arc chute comprises two sections 3@ and 32 that fit together along two edges 34, 3S to form a boxlike enclosure that is open at one end 37 to receive an arc and is open at the other end 3%; to exhaust the cooled and deionized arc residue. Two conductors (arc runners) il and d2 are positioned inside the arc chute along the two edges 34, 35. When the arc chute is in place, one end ot each are runner i-l, it?, snaps onto one of the iixed contact assemblies lil, l?. to provide a conductive path for carrying the ends of the arc from the ixed contacts into the chute. As FlG. 2 illustrates, each section 3d, 32 of the arc chute includes an array of inlike barriers of insulating material that are numbered 4?, a through l, in section 3d and 44, a through l, in section 32. The barriers interleave and thereby lengthen the arc between the two arc runners 4l, 42; and the surfaces and especially the edges of the barriers cool and deionize the arc.

The contactor also includes a magnetic operator 47 for opening and closing the contacts and includes frame members 43 that are arranged to support the elements that have been described.

The general features of the arc chute that have been described so far are conventional, and they show the rela- 'end 38 of the arc chute.

3: tionship between the arc chute and other elements of the contactor that forni the arc and then help to extinguish it. When the improved features of this arc chute are understood, it will be, apparent that the arc 'chute is not limited to circuit interrupters of any particular design or rating.

FIGS. 3 and 4 together show the interior of the two sections 30, 32 of the arc chute. VIn addition to the barriers 43, 44the arc chute includes two side walls 5l), 5l; spacers 53, 54, 55 and 56 that connect the two side Walls ialong the edges 34, 35 of the arc chute; and a pair of ramp shaped members 58, 59 that cooperate to partly close oi the receiving end 37 of the arc chute.

The general features of all of the arc control barriers of FIGS. 3 and 4 can be understood by first considering only the two interleaved barriers 43k yand 44k of FIG. 5.v The arc contacting edge 6i) of the barrier 43k extends from a point 61 near the arc receiving end 37 of its supporting sidewall 50 toward a point 62 on the opposite side wall 51. The arc contacting edge 63 of the barrier 44k extends from the point 61 near the arc receiving end of its supporting side wall 51 toward a point 64 on the opposite side wall Sil. From the points 62, 64 each barrier closely parallels the opposite side wall to the exhaust Between the point 61 and the points 62 or 64 there is a first region in which the edges of the two barriers 43g, 44g gradually converge toward a point 65, and there is a second region between point 65 and points 62, 64 in which the barriers progressively overlap. o

In general, an arc passes through the iirst region (6l to 65) with only slight mechanical impedance but with some cooling and lengthening, and the are is further cooled and is progressivelyflooped and constricted and lengthened in the second region until it is extinguished.

'In the third region (beyond 62, 64) the arc residue is further cooled and deionized so as to prevent a iiashover outside the chute.

The coniiguration of the arc control barriers 43, 44 in the iirst two regions helps the arc chute to loop the are from end to end in the chute, as well as from side to side. `In the second region in particular the arc contacting edges 60, 63 of .the adjacent barriers 43k, 44k differ noticeably from each other. The barrier 43k tapers 'rather gradually toward the opposite side wall 51 and it bridges the two side walls relatively near the exhaust end yof the chute. The barrier 44k of section 32 tapers more sharply toward the opposite wall 59 and it bridges the two side walls relatively near the arc receiving end 37 ofthe arc chute. To heighten the contrast between the two barriers 43k, 44k .the edge 63 .of the more sharply tapered barrier 44k abruptly inclines toward the opposite side wall 50 at a point 67 near the boundary point 61 between the first and second regions of the arcchute, and the more gradually tapered barrier 43k has a cutout 68 that extends along the side wall 5l tolward the exhaust end of the chute.

The other barriers in the two sections 3d, 32 in general.

have the same `features as the two barriers 43g, 44g that have just been described, and the boundary points 61,

62, 64 and 65 extend lfrom one edge of the chute to the other.

Wihen the two sections `30, rl2, of the arc chute are assembled, the barriers interleave to form a labyrinth between the two arc runners 4l, 42. The sharply tapered barriers 44 of the section 32 cooperate with the opposite side wall 50 to form a relatively restricted arc receiving opening extending into the arc chute. The more gradually tapered barriers 43 cooperate with the opposite side wall 51 to form -a less restricted are receiving opening extending into the arc chute. The space between adjacent interleaved barriers is substantially uniform from one end of the chute t-o the other.

TIhe configuration of .the arc control barriers and their arrangement in the chute suggests the probable operation of the chute. As the arc moves into the region in which the barriers interleave, it forms into loops around the tapered edges of the adjacent barriers. Along the more gradually tapered edges ofthe barriers 43 the arc loops move very rapidly into they chute. Along the more abruptly tapered edges of the barriers 44 the arc loops move less rapidly and they fall behind as the arc moves rfartherinto the arc chute. The slight discontinuity 67 in vthe slope of the barriers 44 is particularly eiiectivein slowing the arc near the side wall Sil. As the arc moves into the arc chute, the opening between the edge of the abruptly tapered barriers 44 and the opposite side wall Sil becomes more constricting than the opening between the Vedge ot" the imo-re .gradually tapering barriers `43 and the opposite side 'wall 511. Thus, the arc loops tend -to incline `toward the exhaust along the more gradually I tapering edges of the barriers 43, and the arc loops are .stretched in the relatively unrestricted direction between the ends of the arc chtite as Well as the more limited direction from side t-o side in the arc chute. Tlie boundary 62, 64 `between tbe arc extinguishing region and the region for cooling the arc residue is inclined from side to side and thereby also helps to incline the arc loops. Thel arc tracks of tested arc chutes support this explanation of how the arc chute operates. Y

In the improved arc chute the magnetic tiel-ds of the inclined loops help to drive the arc into the chute. This magnetic blowout .action is independent of the coil 19 and `the magnetic core 20 and pole pieces 2'1, and the blowout action is not limited by saturation of magnetic components as is the coil l19. The magnetic field of any current loop tends to expand the loop. So long as the loops of an arc are in a plane that is normal to the path of the are through the chute, the magnetic field tends to -exipand-the arc loops -outward toiward the closely spaced side walls oi the arc chute. In this arc chute the loops are inclined toward the exhaust and the magnetic tiel-ds Yof the loo-ps tend to expand the loops farther in this direction. Tlhe effe-ct or" the magnetic field on the loops is rather slight at iirst when the loops are only slightly inclined. Since the magnetic `fields of the loops tend to lfurther incl-ine the loops to a more advantageous position lfor the magnetic blowout, the blowout action is progressive and the arc loops incline and expand very rapidly.

In many cases the magnetic lield of the blowout coil 19 and the convection currents that rise through the chute as the are heat-s the dielectric -will counteract the tendency Vtor the arc loops between the more sharply tapering edges of the barriers 44 and the opposite side wall 50 to expand out the receiving end of the arc chute. However, the .arc chute that the drawing illustrates produces i -a violent blowout action, and it is preferable to provide they prevent Ithe arc from blo-wing back onto the contacts.

This invention has been described so far in terms of a rather specific arc chute, but those skilled in the art will recognize that the principles of the illustrated arc chute can be applied to different are chutes of various types. YFor example, one well known type of arc chute has barrier plates that extend from one side of the chute to the other and the barrier plates have slots or other arc receiving openings that correspond to the space between the side walls and the tapered edges of the barriers 43, 44. In such an arc chute one barrier would have a relatively less restricting opening near one side and the next bar rier would have more restricting openings near the other side so that crests of the arc loops would tend to rise rapidlyY through one set of alternate barriers, and they would rise less rapidly through the intervening set of barriers.

Other variations' in the arc chutes that have been described will occur to those skilled in the art, and within the spirit of the invention the claims are intended to include a range of circuit interrupters to which the invention applies.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

1. An arc chute for a circuit interrupter comprising first and second spaced apart generally planar insulating side walls, two spaced apart arc runners for carrying the ends of an arc into the space between said side Walls, and first and second sets of interleaved insulating barriers spaced apart between said arc runners and cooperating with said first side wall and said second side wall, respectively, to define arc receiving -openings near said side walls to distort the arc into a series of loops from side to side, the barriers of said first set and said first side wall progressively constricting the arc receiving openings near said first side wall at a different rate with respect to the movement of the arc through the arc chute than the barriersL of said second set and said second side Wall constrict the openings near said second side Wall to incline the arc in the direction of arc movement in the region of said second side wall.

2. In an arc chute for extinguishing an arc drawn between separating contacts: first and second sets of interleaved insulating barriers spaced apart in the direction of contact separation and having arc contacting edges facing opposite sides of said arc chute to form an arc into a series of loops from edge to edge, said barriers extending in the direction of arc movement in said arc chute,

each of said edges diverging outward from the edges of the adjacent barriers to increase the width of the loops as the arc moves into said arc chute, said edges obstructing the arc movement in the region of an edge according to the inclination of the edge to the direction of arc movement, the edges of said first set more closely paralleling the direction of arc movement than the edges of said second set to incline the arc in the direction of arc movement in the region of the edges of said first set.

3. In an arc chute for extinguishing an arc drawn between separating contacts: rst and second sets of interleaved insulating barriers spaced apart in the direction of contact separation and extending in the direction of arc movement and having arc contacting edges facing opposite sides of said arc chute to form an arc into a series of loops from edge to edge, the edges of adjacent barriers tapering in opposite directions to lengthen the arc as the arc moves through said arc chute, said edges obstructing the arc movement in the region of an edge according to the taper of the edge to the direction of arc movement, the edges of said first set discontinuously tapering from the direction of arc movementto incline the arc in the direction of arc movement in the region of the edges of the barriers of said second set.

4. In an arc chute for receiving an arc at one end and exhausting the are residue at another end: insulating means defining two sides of the arc chute, insulating arc barriers each having an arc contacting edge tapering into the arc chute from near one side of the arc chute to the other side to establish a progressively restricting arc receiving space between each said edge and one of said sides, pairs of said barriers being spaced apart to establish an arc receiving passage between the barriers of'each pair, said passage extending from the receiving end to the exhaust end of the arc chute, said barriers of each of said pairs having their tapering edges facing toward opposite of said sides to stretch an arc from near one side to near the other side, said barriers of each of said pairs having differently tapering edges to stretch the arc from near the receiving end of the arc chute along one of said edges toward the exhausting end of the arc chute along the other of said edges.

5. An arc chute comprising insulating means defining two opposite sides of the arc chute, arc runners positioned near opposite ends of the arc chute to carry an arc into the region between said sides, and a plurality of insulating barriers arranged to loop the arc from side to side around arc contacting edges of said barriers, the arc confcting edges of adjacent barriers and said side walls cooperating to form a region where the arc is progressively looped and constricted as it moves through the arc chute, said arc contacting edges of adjacent barriers being differently shaped throughout said region to restrict the advance of the arc more on one side of the arc chute than on the other side of the arc chute.

6. An arc chute comprising insulating means defining two sides of the arc chute, means for directing an arc into the region between said sides, and first and second sets of arc barriers extending from said sides and interleaved to form the arc into loops around arc contacting edges of said barriers, the arc contacting edges of the barriers of said first set having a relatively high taper and substantially abutting the opposite side wall relatively near the arc receiving end of the arc chute, the arc contacting edges of the barriers of said second set having a relatively shallow taper and substantially abutting the opposite side wall relatively farther lfrom the arc receiving end of the arc chute.

7. An arc chute as defined in claim 6 in which a portion of the arc contacting edges of the barriers of the second set substantially parallel the opposite side wall for a predetermined distance adjacent the abutting point, the distance between the arc contacting edges and the side wall in said parallel portion being suicient to receive the arc.

References Cited bythe Examiner UNITED STATES PATENTS 2,477,189 '7/ 49 Lerstrup 20G-144 2,635,158 4/53 Peter 200-144 2,655,578 10/53 Sillers ZOO-144 2,709,735 5/ 55 Phillips et al 20G-144 2,740,021 3/56 Frink 200-144 BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, E. JAMES SAX, Examiners. 

1. AN ARC CHUTE FOR A CIRCUIT INTERRUPTER COMPRISING FIRST AND SECOND SPACED APART GENERALLY PLANAR INSULATING SIDE WALLS, TWO SPACE APART ARC RUNNERS FOR CARRYING THE ENDS OF AN ARC INTO THE SPACE BETWEEN SAID SIDE WALLS, AND FIRST AND SECOND SETS OF INTERLEAVED INSULATING BARRIERS SPACED APART BETWEEN SAID ARC RUNNERS AND COOPERATING WITH SAID FIRST SIDE WALL AND SAID SECOND SIDE WALL, RESPECTIVELY, TO DEFINE ARC RECEIVING OPENINGS NEAR SAID SIDE WALLS TO DISTORT THE ARC INTO A SERIES OF LOOPS FROM SIDE TO SIDE THE BARRIERS OF SAID FIRST SET AND SAID FIRST SIDE WALL PROGRESSIVELY CONSTRUCTING THE ARC RECEIVING OPENINGS NEAR SAID FIRST SIDE WALL AT A DIFFERENT RATE WITH RESPECT TO THE MOVEMENT OF THE ARC THROUGH THE ARC CHUTE THAN THE BARRIERS OF SAID SECOND SET AND SAID SECOND SIDE WALL CONSTRICT THE OPENINGS NEAR SAID SECOND SIDE WALL TO INCLINE THE ARC IN THE DIRECTION OF ARC MOVEMENT IN THE REGION OF SAID SECOND SIDE WALL. 